1. Field of the Invention
The present invention relates to an end pivot valve train, and more particularly, to an end pivot valve train in which a support protrusion is provided on a cam holder so as to prevent the cam follower from falling towards a rotation axis of a cam during the assembly of the valve train.
2. Description of Related Art
Generally, an engine, particularly, an internal combustion engine is an apparatus transforming thermal energy into a mechanical rotating force. The engine burns fuel in a combustion chamber defined by a cylinder, a cylinder head, and a piston reciprocating in the cylinder to generate explosive force, which rotates a crankshaft through a connecting rod connected to the piston.
On the cylinder head of such an engine, provided are an intake valve for providing a fuel-air mixture to be combusted in the combustion chamber and an exhaust valve for exhausting combustion gas. The intake valve and the exhaust valve are configured to be opened and closed by a valve opening and closing mechanism connected to the crankshaft.
Here, the valve opening and closing mechanism is generally of an overhead valve type and an overhead camshaft type, both of which transform a cam motion of a camshaft, rotatably connected with the crankshaft, into a linear motion of a valve. For the linear motion of the valve along a curve of a cam, the valve is required to always come into close contact with the cam (or an operating device connected to the cam).
The assembly structure of an end pivot valve train of the prior art will now be described with reference to accompanying drawings.
FIG. 1 is a cross-sectional view illustrating the assembly of the end pivot valve train of the prior art, and FIG. 2 is a front elevation view illustrating the end pivot valve train as seen in a direction A.
The end pivot valve train includes a cam follower 110 and a Hydraulic Lash Adjuster (HLA) 130. One end of the cam follower 110 is in direct contact with a stem end 121 of a valve 120 to operate the valve 120 through the rotation of a cam 145. The HLA 130 is in contact with the other end of the cam follower, and serves as a support axis for the cam follower 110 when the cam follower 110 is transmitting a rotating motion of the cam 145 to the valve 120.
Therefore, the cam follower 110 has a support structure such that the opposite ends are respectively supported by the valve 120 and the HLA 130 and a middle portion is supported by the cam 145.
However, such an end pivot valve train has a following problem. Since an assembly process is completed by placing the cam follower 110 on the valve 120 and the HLA 130, placing the camshaft 140 on the cam follower 110, and then installing a bearing (not shown) of the camshaft on the camshaft 140, the cam follower 110 placed on both the valve 120 and the HLA 130 can hardly maintain the steadily-supported position during the connection with the camshaft 140.
That is, since there is no means for securely supporting the cam follower 110, with one end of the cam follower 110 in contact with the stem end 121 of the valve 120 and the other end of the cam follower 110 in contact with the upper portion of the HLA 130, the assembled state of the cam follower 110 may be made unstable by a force acting in other directions than a vertical direction during the assembly process of the camshaft 140.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.